MEa Benchmark Assessment

Test Essay Quality Points

Chemical vs. Physical Change

• Chemical vs. Physical Change.
• Chemical Change involves changing chemical bonds.
• Physical Change can involve change of state, but no changing chemical bonds.
• Chemical Change can be reversed, but energy input is required.
• Examples provided for each.
  • 5 Points: When you melt a rock, it is just a physical change. Once the rock cools and solidifies, it would be rock again. When you smelt ore, the elements actually separate from one another, getting rid of the bond that made that specific ore. This is a chemical change. One difference would be that, after melting rock, it would become rock again, where as smelting ore separates the two elements in a chemical change. A similarity is that they can both be reversed. For example: a rock melted into lava, once cool, would turn to rock again, and iron exposed to air for a long time creates rust, turning it back into iron oxide.

Polymers

• Plastics come in different varieties.
• Different plastics are chosen for their different physical properties.
• Plastics are polymers, repeating chains of monomer units.
• Plastics are constructed primarily of long chains of carbon atoms.
• Mixing different codes results in a tangle of different polymers, without their distinctive characteristics that make them valuable.
  • 5 points: Plastics have different codes because each type of plastic is a different polymer. Polymers are long chains of monomers and they are very different from each other. It is a good idea to separate plastics into their separate types when recycling because when you put two different types of plastics together they form a lower quality plastic than a plastic made of one polymer type. This process is called downcycleing and is best to be avoided.

Introduction to Balance